Gauss type photographic objective consisting of five lens elements arranged in four components



SR N SEARCH RO( y 1962 JIRO MUKAl 3,033,080

GAUSS TYPE PHOTOGRAPHIC OBJECTIVE CONSISTING OF FIVE LENS ELEMENTS ARRANGED IN FOUR COMPONENTS Filed 001:. 27, 1958 Fl 6. I

v -2 o 2% -o.oo5 o 0.005mm -o.o\ 0 pm S PHERICAL ABERRATION IMAGE CURVATURE IMAGE DISTORTION INVENTOR.4 J/RO Mum/ BY v Ant/rm GAUSS TYPE PHOTOGRAPHIC OBJECTIVE CON- SISTING OF FIVE LENS ELEMENTS ARRANGED IN FOUR COMPONENTS Jiro Mukai, Yokohama City, Japan, assignor to Canon Cfamera Company, Inc., Tokyo, Japan, a corporation apan Filed Oct. 27, 1958, Ser. No. 769,802 1 Claim. (Cl. 88-57) This invention relates to Gauss type photographic objectives consisting of five lens elements arranged in four components.

A photographic objective having an aperture ratio of about 121.8 and having an image field of about 50 degrees usually consists of six or more lens elements. Such number of lenselements is considered necessary to correct the various aberrations of photographic objectives of high quality in the prior designs.

An object of this invention is to provide a photographic objective consisting of five lens members and having better correction than the prior and conventional objectives comprising six or more lens elements.

A clear concept of the scope and purpose of this invention may be obtained from the following description taken in connection with the attached drawing in which:

FIGURE 1 is a sectional view of a photographic objective according to this invention;

FIGURE 2 represents the spherical aberration of the objective;

FIGURE 3 represents the image curvature of the objective; and

FIGURE 4 represents the distortion of the objective.

The features of the construction of the photographic objective according to the present invention are' as follows:

The photographic objective consists of five lens elements arranged in four air spaced components of which the first component is a single positive meniscus lens with its convex surface directed to the object side. The second component is a negative meniscus component consisting of a front bi-convex and a rear bi-concave lenses cemented together and giving a negative action by the cemented surface. The third component is a single negative meniscus lens with its concave surface directed tothe object side. The fourth component is a single bi-convex lens. Furthermore, the objective meets the following conditions,

, the axial [thicknesses of the lens ele-,

Example [Focal length f=1. Aperture ratio 1 1.8. Angular field d =0. 139 N l. 6228 Vs=56. 9 Rl= 3. 294

da=0. 043 Na=1. 7400 Va=28. 2 Rs=0. 241

Si=0. 102 Rs= -O. 566

dl=0. 171 N4=1.6080 V4=46.2 R1= -1. 140

Ss=0.004 RIF-11. 880

d =0. 071 Ns=1.74400 Vs=44.90 Ro= 0. 871

The aberrations of the above example are shown in FIGURES 2 to 4. In FIGURES 2, S and S represent the spherical aberrations for the d and g lines of the spectrum, respectively, and 8' and S, represent the deviation from the sine condition for such lines. In FIGURE 3, A and A represent the image curvatures on the sagitt-al and meriodional planes, respectively. 'In FIGURE 4, D represents the distortion. These curves show the quality of the objective.

A photographic objective consisting of five lens elements arranged in four components wherein the third component is a single lens is not entirely a new thing in the Gauss type objective. However, in such conventional lens, the aberrations are not corrected to a sufficient extent, especially as to coma and as to chromatic aberrations, and, in addition, it is diflicult to obtain a large image field for the objective.

The objective of my invention based upon the Gauss type objective consisting of six lens elements, andthe effect obtained by the cemented surface in the third component of the prior Gauss type objective is transferred to another component in my improved objective so that the third component becomes a single lens and with the objective retaining the same or a higher efliciency. The positive refractive action given by the conventional cemented surface in the third component is replaced by making the In the prior known Gauss type objectives, chromatic aberration is corrected by the cemented surface in the third component, but in an objective according to my invention, chromatic aberration is eliminated by giving a value higher than 45 to the dispersive index of the optical material of the convex lens of the second component. Thus by this invention, in spite of the reduction of the number in lens elements as a whole, a photographic objective well corscripts increasing from the front to the rear of the objective. 1

rected for aberrations and having an image field of about 50 degrees is obtained.

'What I claim is:

A photographic objective having a relative aperture at least as large as f/ 1.8 and a field angle of at least 46 4 which is highly corrected for coma and chromatic aberwhere Rimming is the radius of curvature of the successive ration according to the following numerical data: lens surfaces, dsubsmpt the axial thickness of the successive lens elements, Ssubsmpt the spacing between successive [Focal z f= Apertummio f/ u ar field 6l I lens elements, Nsubsmpt the refractive index of the glass of 5 the successive lens elements, and Vsubsmpt the Abbe num- Radius 01' Axial Index 0! Abbe her of the glass of the successive lens elements, the sub- Cm'vatum fil gfifi Refmmn Number scripts increasing in the direction from the object side of the objective. y t I 0-600 dFOMD N|=L7234 VFW) 10 References Cited in the file of this patent RP 3-565 UNITED STATES PATENTS 0-354 2487 749 Wynne Nov 8 1949 a =o.139 N =1.6228 v =56.8 1 n R4=-3.294 2,499,264 Wynne Feb. 28, 1950 R5: 0.241 NPl-m 2,672,778 Brendel Mar. 23, 1954 S4=0.162 1 2,683,398 Klemt etal July 13, 1954 m i=0," mama, =46, 2,777,362 Berger 61 al. Jan. 15, 1957 R1=1.140 2,818,776 Hayes et a1 Ian. 7, 1958 2,831,395 Klemt Apr. 22, 195s 2o FOREIGN PATENTS 963,687 France Ian. 12, 1950 

